Moisture responsive signaling device



Feb. 2, 1954 a. D. KAPLAN MOISTURE RESPONSIVE SIGNALING DEVICE FiledAug. 2, 1952 INVEN TOR. BENJAMIN D. KQPMN 1.

\ 4 I orne Patented Feb. 2, 1954 UFNFI TILED S TATE S FATE-N T O F -F'iCE MOISTURE'RE SPONSIVE SIGNAEINGDEVIGE Benjamin DrKaplan Bux-bankGalif.

Application August 2, 1952,SerialNo. 3021310 -9 laims. (Cl.20.0--'.61".05')

This invention relates to signaling devices and more particularly tosignaling devices adaptedto give a signal when affected by moisture.

Several-devicesoi the abovenature h-ave'been proposed for giving asignal when exposed to moisture "such as rain or partially conductiveliquids in one form or another. For examplathe systems find'use ininforming an attendant of the wettingof a-bed'or bed-clothes by them:-cupant thereof. The devices have generally compriseda pair of flexibleflat coplanar'electrodes mounted on or inibedded in an insulative padmember Whichmay be placed in aninfants bed, or ina location where thepresence of moisture isdesired'to be detected. Theelectrode-surfaceedges are'disposedjadjacent one another in such "a "manner 'that'aconducting liquid on the pad surface will electrically 'bridge and shortcircu'itthe electrodes to "complete "apower circuit. The signalingmechanism itself, such as .a hell or light, .forexample, may be actuatedby a'reiay in the power circuit. To increaseithe arearesponsive to themoisture, the electrodes have been interleaved in such a mannerthatthe'short circuitine canbe effected at several diflerent portions onthe pad member surface.

While these prior systems have been satisfactory 'to some extent, theyhave tended to be bulkyand cumbersome. Further, the'interleaving typeelectrode-design lengthens considerably the electrical path that'thecurrent must follow. This is especially the case when the short circuitis efiected at apoint on the pad spaceda considerable distance from theelectrode terminals. In the interests of flexibility and portability,the electrodes must necessarilybe'thin in their third dimension. Thisadditional path length therefore offersa high resistance to currentIflow and consequently reduces the reliability of the device. Thus, forexample, while theactual current flow between the electrodes necessaryto actuate a relay is generally quite small, the conductivity of theactuating liquid may be so poor that its resistance in series with anyadditional resistance due to the interleaving electrode structure, isoftentimes sufficient to prevent the current from actuating thesignaling mechanism.

An additional difficulty Withthese paststruc tures is that in order toinsure that the electrode interleaving edges are insulated from oneanother, an appreciable space between these edges would have to bemaintained. This is because these electrodes have in the past .taken theform of metal foil or conductive fiat strips glued or otherwise'secured' tothepad member surface and thus subject to slippage "intocontact with one another, especially "during the moulding or 2securing'proeess. The effectiveness of the moisture pad is impaired by a"large space to be bridged by the liquid since the resistance paththrough the liquid is greatly increased.

It 'is an object of the present "invention, accordingly, to provide amoisture responsive device which is considerably more flexible andportable than has "characterized prior designed systerns, and yet *isextremely *reliable in its electrical operation.

More particularly'it i's an objecto'f the invention to provide "animproved "moisture responsive pad-of the type "described 'in'wh'ichthe'electrical resistance "or current paths in the electrodesisminimized.

A further "object is to "provide a "signaling clevice in which "theelectrode :array and pad is such as to render the system'many times moresensitive to moisture "than has been :achieved in the past.

These and other objects of the invention are attained "by providing whatmay be termed .a three dimensional typemoisture responsiveipa'ol in"contra-distinction to the ftwo dimensional prior systems in which theelectrodes were coplanar. In general, the invention comprises a flexiblefiat pad meniberl'hav'ing deposited on one surface thereof aconductingmaterial .constituting a first electrode o'irelativelylargesurface area. ZPortionsof this .letrodesurffaceare coveredby aninsulatin-glmaterial. This insulating material .may be treated .with asalt bath such.that:anylliquidlfalling on it will -.be rendered at leastpartially conductive. The insulating material in .turn Ilhasdeposit-edon itssurfacea conducting material constituting a second elec-- trode.The electrodes. rethu sp d par y a thickness corresponding to .thethickness of the insulating material, in substantially parallel planes.when thepad. :member .is :lyingflat. The portions ofthelfirst.electrodesurfaeenot covered by .the insulating material areexposed so that any moisture .on :the .pad member surface will readilyeffect a=short oircuit between the electrodes.

:In a specific :embodiment, zthe insulating lma terial may takef-theiorm .of a zdetachableeec- 0nd flexible pad .member upon which thesecond electrode:maybeeasily deposited. .On the other hand, .theinsulating material may constitutean .insulative coating spread directly.on portions of the Ifirst electrode surface, the second electrodesurfacebeing deposited on this coating tofiorm an integral unit.

With either .of these arrangements "it "will "be seen :at once that theelectrical path -resistance through *the electrodes is materiallyreduced be- 3 cause of the infinite number of parallel paths the currentcan follow on each electrode to the terminals of the pad member.Furthermore, the feature of depositing the electrodes directly on thepad member and insulative material provides a device which is extremelyflexible and portable.

A better understanding of the invention will be had by referring to theaccompanying drawings, in which:

Fig. 1 shows in perspective one embodiment of the moisture pad andelectrode arrangement;

Fig. 2 is an enlarged edge view of the pad member of Fig. l as anassembled unit;

Fig. 3 illustrates a top view of another embodiment of the inventiontogether with a schematic diagram of the alarm circuit;

Fig. 4 is a cross-sectional view as seen along the line 44 of Fig. 3;

Fig. 5 shows in perspective still another form the moisture pad may takein accordance with the invention.

Referring to the drawings, there are shown signaling devicesparticularly suited for indicating the wetting of a bed by an infant,for example. For this purpose, it is desirable that the moistureresponsive pad be light, rugged, and extremely flexible so that when itis laid flat in a bed or crib its presence will not be uncomfortable tothe occupant. While features of the present invention render thesignaling device as shown in the drawings particularly suitable for thisparticular use, the invention is not to be thought of as limited solelyto this application.

In Fig. l the device is shown as comprising a flexible pad member Ii!having a first electrode I I on its upper surface as shown. Althoughelec trode II is preferably formed by depositing conductive materialdirectly on the pad member surface, it may, instead, constitute aflexible metal foil secured to or imbedded in the surface of the pad. Ametallic terminal I2 secured to an extension II of electrode II passesthrough pad member Ill and is adapted to be electrically connectetd to acooperating terminal I2 on a detachable cord support I3.

A second pad member I4 made of insulative material adapted to coverpartially electrode II has deposited or imbedded on its upper surface asecond electrode I5 as shown. Electrode I5 also includes an extension[5' to which a metallic terminal I B is secured and adapted to extendthrough pad I4 and a cooperating opening in pad Ill (not shown) to asecond terminal I5 on the cord support I3. Pad member I4 also includesat each of its four corners snap means cooperable with correspondingsnap sockets on the corners of the lower pad member III. Thisarrangement permits the pad members to be secured together andcorresponding electrodes to be connected to a cord extension leadingfrom cord support I3. Cord extension I! terminates in a jack I8 whichmay be conveniently plugged into an alarm circuit. Clearly, other meansfor securing the two pad members Ill and I4 may be employed. The featureof making the two pads separable facilitates cleaning the electrodesurfaces.

One or more openings I9 passing through the second electrode i5 and padmember I4 are provided so that only a portion of the first electrodesurface II is covered when the various elements are assembled. Portionsof the first electrode II are thus exposed through openings I9 when padI I is covering the pad I0.

Fig. 2 shows the assembled unit from one end in exaggerated dimensions,the same reference numbers designating the corresponding elements shownin Fig. 1.

In operation, the assembled unit may be laid fiat in an infants cribunder the main sheet for example, and the extension cord ll connected toa suitable alarm circuit. Wetting of the bed clothes or diapers by theinfant will thus moisten the upper surface of the electrode I5 and theexposed surface of electrode I I through openings I9 providing aconducting path between the electrodes. This action completes a powercircuit which may contain a relay to operate a buzzer or light andinform an attendant of the wetting, .or awaken the child.

Fig. 3 discloses such a circuit arrangement in schematic form connectedto a modified type of moisture responsive pad. In this embodiment, aflat pad member 30 similar to pad ID in Fig. 1 has a first electrode 3|deposited on its surface. Electrode 3| is partially covered by anelectrically insulative coating 32, such as a suitable insulating paint,as shown in the cross-sectional view of Fig. 4. A second electrode 33 isdeposited on the surface of the insulative paint, the electrodes 3| and33 being respectively provided with extensions 3| and 33' for connectionto a suitable signaling circuit. A plurality of openings 34 in theelectrode 33 and insulative coating 32 leave substantial portions of thesurface of electrode 3| exposed such that the electrodes 3| and 33 arereadily short circuited by any moisture or liquid falling on the surfaceof pad member 3|].

The associated power circuit may comprise a battery 35, relay coil 36and switch 31 connected in series between the electrodes 3| and 33 asshown. Operation of the relay arm 36 serves to connect a signalingelement, such as a light or buzzer 38, across the battery 35 by closingcontact 39.

With this arrangement, and switch 31 closed, wetting of the pad member30 will electrically connect the electrodes 3| and 33. Current frombattery 35 will then flow around the circuit, operating relay 36 toclose contact 39 and actuate the signaling element 38.

Fig. 5 discloses yet another form the invention may take. In thisembodiment a flexible pad member 58 of insulating material has a firstelectrode 5| deposited or otherwise secured to one surface of the pad. Asecond electrode 52 is similarly applied to the opposite surface of thepad. As in Figs. 1 and 3, suitable electrode extensions 5| and 52 may bprovided for connection to a suitable alarm circuit 53.

A plurality of openings 54 extending through both electrodes 5| and 52and pad member 50 permit any moisture or liquid to electrically shortcircuit electrodes 5| and 52 when the pad member is lying on a bed sheetor mattress. This action obtains because of the absorbing nature of thesheet or mattress which serves to moisten the bottom electrode 52 frommoisture passing through the openings 54.

In the various forms of the invention as illustrated in Figs. 1 to 5,the flexible pad member may comprise poly-vinyl chloride, known underthe trade name of Vinylite. This material is highly flexible and hasgood electrical insulating properties. The electrodes themselves maycomprise silver, deposited directly on the surface of the Vinylite. Asuitable screening material may be used when applying the insulativepaint and second electrode to the pad member in Fig. 3 to provide theopenings 34.

It will be appreciated that the embodiments disclosed in Figs. 1 to 5provide a highly flexible and rugged moisture-responsive signalingdevice. Further, the reliability of operation of the pad member in thepresence of only small quantities of moisture is greatly enhanced due tothe extremely close spacing of the electrodes. This close spacing ispossible because of the three dimension construction feature wherein theelectrodes are separated only by the thickness of the insulatingmaterial.

By providing a plurality of registering openings in the second electrodeand th insulative layer thus exposing portions of the surface of thefirst electrode, the electrical bridging of the two electrodes by anymoisture laden bed clothes or liquid on the pad surface is readilyeffected. in the case of the wetting by an infant, the salt in its urineis sufficient to provide a partially conducting liquid. On the otherhand when the insulating material has been treated in a salt bath forexample, any liquid such as rain will be rendered conductive uponfalling on the pad. It should be understood of course that openings ofany suitable configuration may be employed. The circular and elongatedslot openings depicted in Figs. 1 and 3 respectively are shown merely byway of example. It is preferable to have the openings distributed over alarge area of the pad surface so that moisture falling anywhere on thesurface will eifect the short circuit.

It is also to be appreciated that the particular electrode arrangementprovides a low resistance path from the point where the electrodes areshorted to the terminal points on the pad. This is because the wholesurface of each pad respectively is utilized to conduct current to thepad terminals. Thus each pad surface effectively provides an infinitenumber of paths in parallel leading to the respective terminal. Also,these pads do not necessitate the use of molds or dies in theirmanufacture.

Various modifications within the spirit of the present invention willreadily occur to those skilled in the art. Thus, while snap means havebeen disclosed in Fig. 1 for assemblying the various elements, any othersuitable fastening means may be employed. For example, the extensioncord may be directly secured to the electrodes by any suitableconnecting means. Also, it is not necessary that the respective pads befastened together; one may simply rest flat on top of the other.Further, the electrodes may constitute any type of flexible conductingmaterial secured to or imbedded in the insulative surfaces, such asmetal foil for example. Any suitable alarm circuit or responsivemechanism may also be substituted for the circuit of Fig. 3 such as asensitive electronic circuit wherein the sensitivity of the device maybe greatly increased by feeding the signal to the control grid of avacuum tube.

Moreover, while the apparatus has been described in detail withreference to a signaling device for indicating the wetting of a bed, theinvention has many other useful applications. For example, it may beused to actuate window or door closing mechanisms in response to raindrops falling on the pad member.

The invention therefore is not to be thought of as limited to theprecise embodiments disclosed.

I claim:

1. A moisture responsive device comprising a flexible pad member made ofelectrical insulating material, a first electrode comprising acontinuous layer of electrically conducting material on one surface ofsaid pad member, and a second electrode containing a plurality ofopenings therethrough on the opposite surface of the pad member wherebythe first and second electrodes are spaced apart by said pad member insubstantially parallel planes when the pad member is lying flat.

2. A device according to claim 1, in which said electrodes compriseconductive metal foil secured to the opposite surfaces of said padmember respectively.

3. A signaling device comprising a flexible pad member, a firstelectrode deposited on one surface of the pad member, electricalinsulating means comprising an insulative-coating covering portions ofsaid first electrode, a second electrode deposited on only thoseportions of the insulative coating covering the first electrode, wherebythe portions of the first electrode not covered by the insulativecoating are exposed.

4. A moisture responsive device comprising in combination: a firstflexible pad member, a first electrode on at least one surface of thepad member, a second flexible pad member made of electrical insulatingmaterial and containing a plurality of openings therein distributed overa substantial area of the second pad member, a second electrode coveringsaid second pad member and containing openings registering with thefirst mentioned openings, means for securing the second pad member tothe first pad member whereby the first and second electrodes are spacedapart by said second pad member and portions of the first electrodesurface are exposed through said openings.

5. A device according to claim 4, in which said electrodes are imbeddedin said pad members.

6. A moisture responsive device comprising a flexible pad member, afirst electrode deposited on one surface of the pad member, electricalinsulating means coated over portions of the first electrode whereby aplurality of openings exposing other portions of the first electrodesurface are distributed over a substantial area of the surface, a secondelectrode deposited on only those portions of the insulative coatingmeans covering the first electrode surface, whereby said electrodes areelectrically insulated from each other by said insulative coating means.

'7. A moisture responsive device comprising a first electrode made ofconductive material in the form of a fiexible pad, a second electrodesimilar in dimensions to said first electrode and containing a pluralityof openings therethrough extending over a substantial portion of itsarea, said second electrode being adapted to lie over said firstelectrode, and electrical insulating means disposed between saidelectrodes.

8. A device according to claim 7, in which said first electrodecomprises a continuous conductive layer, conducting portions thereoflying directly beneath said openings in the second electrode.

9. A device according to claim 8, in which said insulating meanscontains a plurality of openings registering with the openings in saidsecond electrode whereby said conducting portions are exposed.

UNITED STATES PATENTS Name Date Van Guilder Aug. 5, 1930 Number

